VT17
Structural
- Apr 27, 2018
- 14
Hello All,
I'm designing a post tensioned parking deck in ADAPT Builder, and I believe I have all the typical PT beams and slabs working fine for stresses, precompression, and balanced loading. However, I have some girders at the end bays of the parking deck supporting a beam that I'm having trouble getting to work. These girders have a harped tendon profile with the low point at the location of the beam it's supporting. Please see the attached framing sketch.
I have the girders working for top and bottom stresses as well as for precompression. However, my load balance percentage is quite high at about 200%. I've been playing with the number of tendons and the elevation of key points of the harped profile (mainly the low point), but if I reduce the number of tendons or raise the low point of the harped profile, I end up with the bottom stresses near midspan not working while still not getting the load balancing below around 150%.
Do any of you have any advice or guidance as to what variables I should concentrate on modifying to reduce the load balance percentage while maintaining my top and bottom stresses to an acceptable range? I would prefer to not change the size of the concrete girder. I'm looking for general advice as to which variables affect the load balancing the most as running analysis for PT is not the fastest thing for me.
The information shown in the sketch assumes 5ksi concrete, 1/2" tendons with an effective force of 27kip per tendon. Thank you in advance!
I'm designing a post tensioned parking deck in ADAPT Builder, and I believe I have all the typical PT beams and slabs working fine for stresses, precompression, and balanced loading. However, I have some girders at the end bays of the parking deck supporting a beam that I'm having trouble getting to work. These girders have a harped tendon profile with the low point at the location of the beam it's supporting. Please see the attached framing sketch.
I have the girders working for top and bottom stresses as well as for precompression. However, my load balance percentage is quite high at about 200%. I've been playing with the number of tendons and the elevation of key points of the harped profile (mainly the low point), but if I reduce the number of tendons or raise the low point of the harped profile, I end up with the bottom stresses near midspan not working while still not getting the load balancing below around 150%.
Do any of you have any advice or guidance as to what variables I should concentrate on modifying to reduce the load balance percentage while maintaining my top and bottom stresses to an acceptable range? I would prefer to not change the size of the concrete girder. I'm looking for general advice as to which variables affect the load balancing the most as running analysis for PT is not the fastest thing for me.
The information shown in the sketch assumes 5ksi concrete, 1/2" tendons with an effective force of 27kip per tendon. Thank you in advance!
